Like a handwritten signature, a document's digital signature (also known as a digital ID or digital profile) represents you to the recipient. A digital signature has two parts: a public key and a private key. Fortunately, you don't have to decide which key to use when. You use your private key to apply your digital signature to a file, which encrypts the data by using the public key. The public key is contained in a certificate that you exchange with your colleagues and contacts to verify your identity. Other people use your public key to create encrypted information to share with you. This two-way exchange of certificates and keys is the basis for building trusted identities (discussed later in this article).
Creating a Signature
You can create both default and custom signatures in Acrobat. To create a new signature, follow these steps:
- Choose Advanced > Security Settings to open the Security Settings dialog box. Click Digital IDs on the left side of the dialog box to display your existing ID files in the upper-right pane of the dialog box (see Figure 1).
Figure 1 Digital ID files, along with other types of security servers and IDs, are listed in the Security Settings dialog box.
- To build a new signature, click Add ID on the dialog box's toolbar. The Add Digital ID dialog box opens, giving you four options. The first three deal with existing IDs: You can find an existing ID from a file, a roaming ID stored on a server, or a device connected to your computer (such as a smartcard). To build a new ID, click "A new digital ID I want to create now" and then click Next at the bottom of the dialog box.
- On Windows, the next dialog box asks where you want to store the digital ID. You have two choices: The default option is to create a new PKCS #12 digital ID file, or you can add the digital ID to your Windows certificate store. Click an option, and then click Next.
- In the next dialog box, add the information you want to include in the certificate, such as name, organization name, and email address.
- At the bottom of the dialog box, select a key algorithm, which defines the level of encryption and the version of Acrobat that can open the file. Choose 2048-bit RSA for Acrobat 9, or 1024-bit RSA for Acrobat 7 or 8.
- From the "Use digital ID for" menu, choose the appropriate option:
- Digital Signatures
- Data Encryption
- Digital Signatures and Data Encryption
- Click Next. In the final pane of the dialog box, click Browse to choose a storage location for the certificate, or leave the default location in the Security subfolder of the Acrobat program's installation folders so that you don't lose track of your certificates. Type a password and a confirmation of the password, and click Finish.
- Close the Security Settings dialog box.